过渡金属催化多氟芳烃碳氢键直接官能化

多氟芳烃衍生物是一种在医疗和有机半导体材料等方面有重要用途的化合物。本文介绍了近8年来过渡金属钯、铑、铜、镍催化多氟芳烃碳氢键直接官能化反应的进展。     

阴离子协助镍催化碳氟键官能团化反应机理研究

由于碳-氟键的化学惰性,其高效催化转化一直是有机化学中的难题之一.本文运用密度泛函理论(DFT)计算,研究了镍催化碳-氟/碳-氢键交叉偶联反应构建2-芳基噁唑衍生物的机理.计算结果表明,体系中氟负离子能够稳定零价镍金属催化剂,得到氟负离子配位的阴离子镍活性催化物种.在氟负离子协助下碳-氟键对阴离子镍氧化加成得到二价芳基镍物种,是催化循环的速控步骤.在碳氢键切断过程中,Br?nsted碱直接进攻去质子,得到二芳基镍中间体,最终通过还原消除得到交叉偶联产物.在这一过程中,阴离子镍活性催化物种的稳定性明显高于通常推测的中性镍催化物种,这一模型为理解惰性碳-氟键活化反应机理提供了新的思路.     

烯基自由基参与的分子内氢原子转移反应的新进展

近年来烯基自由基引发的氢原子转移反应受到了广泛的关注.利用该策略可以实现自由基成环反应和区域选择性的远程sp3碳氢键官能化反应,包括碳氢键烯基化、炔基化、卤化及芳基化等反应.在该类反应中,烯基自由基的产生方式由传统的烯基卤化物单电子还原,拓展到通过外加自由基对炔基的加成.这些反应依据底物类型的不同,机理路径也有所不同....     

金催化的双sp~3-C—H活化/C—C偶联反应研究

近年来,均相金催化的惰性碳氢键官能化研究已成为有机合成领域的一个热点.但是它们大多局限于不饱和碳氢键,而且经常需要使用合成氧化剂,这些局限性大大降低了金催化的实用性.从绿色化学的角度而言,空气是大自然界最理想的绿色氧化剂     

配体促进的过渡金属催化芳烃远程meta-C—H键官能化反应研究进展

过渡金属催化C—H活化反应中,配体能够对催化中心的空间及电子效应进行调控,从而实现芳烃C—H键的选择性官能化.近年来,配体促进芳烃远程C—H键官能化反应研究有了新的进展.对近几年来配体促进的过渡金属催化芳烃远程meta-C—H键选择性官能化反应进行了系统总结,并对该研究领域的局限性和未来的发展前景进行总结和展望.     

各类手性质子源及其在去消旋化反应中的应用

介绍了近２０年来利用各类手性质子源，通过对应选择质子化进行去消旋化反应的研究进展。     

无过渡金属条件下喹啉C5位碳-氢键官能化反应

喹啉是一类重要的杂环化合物,喹啉类化合物的合成方法研究备受关注。通过喹啉的碳-氢键直接官能化反应制备取代喹啉类衍生物是一种简便而有效的方法。然而,喹啉的C5位选择性碳-氢键官能化反应仍然存在挑战,目前大多在过渡金属催化下实现,无过渡金属条件下的反应亟待开发。本文按成键类型(碳-卤键、碳-氮键、碳-氧键、碳-硫键和碳-碳键)分类综述了近年来在无过渡金属条件下喹啉C5位碳-氢键官能化反应的研究进展,并对该领域的研究现状及所存在的问题进行了总结。     

过渡金属催化的酮羰基导向C—H键官能化反应进展

近二十年来,过渡金属催化的酮羰基导向C—H键活化已发展成为在酮的非传统反应位点构建碳碳键和碳杂键(杂原子为氮、氟和氧原子等)的强有力而快捷的手段.其中,钌、铑、钯、铱等贵金属催化的酮羰基导向C—H键活化反应得到了广泛研究,而廉价3d金属锰、铁和钴催化的酮羰基导向C—H活化反应逐渐成为当前研究的热点.文中按照过渡金属催化的酮羰基导向C—H键官能化的不同反应类型(烷基化、烯基化、酰胺化、芳基化、环化等)综述了该领域近年来(2014～2021)的研究进展.     

基于四配位硼的1,2-迁移反应研究进展

有机硼化合物是合成方法学中重要且通用的合成骨架.由于其独特的性质,它们在有机合成中表现出巨大的价值.有机硼化合物具有丰富的转化能力,近年来,由于其迁移反应高效、反应条件温和而受到了化学家们的广泛关注,用于快速构建各种碳碳键和碳杂键.本篇综述根据不同的反应条件和键的形成,系统总结了近年来基于四配位硼中间体的1,2-迁移反应.     

羰基兼容的氟代反应及远端氟代脂肪酮合成的近期进展

含氟化合物在医药、农药以及材料领域有着广泛的应用, 然而温和而高效的构建sp³碳氟键却极具挑战性. 氟代脂肪酮类化合物是一类重要的含氟合成砌块. 本文将从碳氢键氟化、脱羧脱硼氟化、双键氟化、开环氟化四个方面简要概述近年来羰基兼容的氟代反应以及在合成远端氟代脂肪酮方面取得的重要进展.     

Iridium-catalyzed silylation of unactivated C–H bonds

The functionalization of primary C–H bonds has been a longstanding challenge in catalysis. Our group has developed a series of silylations of primary C–H bonds that occur with site selectivity and diastereoselectivity resulting from an approach to run the reactions as intramolecular processes. These reactions have become practical by using an alcohol or amine as a docking site for a hydrosilyl group, thereby leading to intramolecular silylations of C–H bonds at positions dictated by the presence common functional groups in the reactants. Oxidation of the C–Si bond leads to the introduction of alcohol functionality at the position of the primary C–H bond of the reactant. The development, scope, and applications of these functionalization reactions is described in this minireview.     

光/电化学氧化诱导C–H键官能团化

C–H键活化及其官能团化一直被认为是合成化学的圣杯,光/电氧化诱导C–H键官能团化反应为追求更为绿色、原子经济性、步骤经济性更高的现代合成化学提供了新思路.我们借助可见光或电化学氧化诱导策略实现了直接C–H键官能团化,即底物无需预官能团化,无需外加氧化剂,可直接实现碳–碳以及碳–杂键的构建.通过光/电化学氧化诱导策略使得反应在更为温和的条件下进行,能够兼容更多官能团,并且为合成化学提供一条新的途径.近些年,该策略已经应用于不同化学环境C–H官能团化构建多种化学键.本文结合该领域的代表性工作,重点介绍本课题组近些年在光/电氧化诱导C–H键官能团化反应上的研究进展,并对这一领域的前景进行了展望.     

A new anion receptor utilising aromatic and aliphatic C…H hydrogen bonds

We have synthesised 2, which bound weakly basic halide ions only with C–H…anion hydrogen bonds. Compound 2 utilised one aromatic C–H hydrogen bond and one benzylic C–H hydrogen bond to bind weakly halide ions such as chloride, bromide and iodide in solution. Ab initio calculations of binding energy values for these anions are in good agreement with experimental data. Although the binding affinities of 2 for these anions were low, 2 could be a unique example of host, which utilised only C–H hydrogen bonds to bind anion.     

Oxidation‐Induced C—H Functionalization: A Formal Way for C—H Activation

Cross‐coupling reactions have developed widely and provided a powerful means to synthesize a variety of compounds in each chemical field. The compounds which have C—H bonds are widespread in fossil fuels, chemical raw materials, biologically active molecules, etc. Using these readily‐ available substances as substrates is high atom‐ and step‐economy for cross‐coupling reactions. Over the past decades, our research group focused on finding and developing new strategies for C—H functionalization. Compared with classical C—H activation methods, for example, C—H bonds are deprotonated by strong base or converted into C—M bonds, oxidation‐induced C—H functionalization would be another pathway for C—H bond activation. This perspective shows a brief introduction of our recent works in this oxidation‐induced C—H functionalization. We categorized this approach of these C—H bond activations by the key intermediates, radical cations, radicals and cations.     

Electrophotocatalytic Decarboxylative C−H Functionalization of Heteroarenes

Decarboxylative C−H functionalization reactions are highly attractive methods for forging carbon–carbon bonds considering their inherent step- and atom-economical features and the pervasiveness of carboxylic acids and C−H bonds. An ideal approach to achieve these dehydrogenative transformations is through hydrogen evolution without using any chemical oxidants. However, effective couplings by decarboxylative carbon–carbon bond formation with proton reduction remain an unsolved challenge. Herein, we report an electrophotocatalytic approach that merges organic electrochemistry with photocatalysis to achieve the efficient direct decarboxylative C−H alkylation and carbamoylation of heteroaromatic compounds through hydrogen evolution. This electrophotocatalytic method, which combines the high efficiency and selectivity of photocatalysis in promoting decarboxylation with the superiority of electrochemistry in effecting proton reduction, enables the efficient coupling of a wide range of heteroaromatic bases with a variety of carboxylic acids and oxamic acids. Advantageously, this method is scalable to decagram amounts, and applicable to the late-stage functionalization of drug molecules.     

Recent advances in mechanochemical C–H functionalization reactions

The mechanochemical synthesis has provided a greener alternative to solution-based approaches by eliminating the use of organic solvents and reducing the energy consumption. The C–H functionalization is among the most concise and economical synthetic strategies. The combination of the benefits from these two methods provides new opportunities to further increase the efficiency and sustainability of organic synthesis. In this digest, we aim to provide a brief overview of the recent advances in mechanochemical C–H functionalization reactions.     

Arenes and Heteroarenes C−H Functionalization Under Enabling Conditions: Electrochemistry,Photoelectrochemistry & Flow Technology

C−H bond functionalization generates molecular complexity in single-step transformation. However, the activation of C−H bonds requires expensive metals or stoichiometric amounts of oxidizing/reducing species. In many cases, they often require pre-functionalization of starting molecules. Such pre-activating measures cause waste generation and their separation from the final product is also troublesome. In such a scenario, reactions activating elements generating from renewable energy resources such as electricity and light would be more efficient, green, and cost-effective. Further, incorporation of growing flow technology in chemical transformation processes will accelerate the safer accesses of valuable products. Arenes & heteroarenes are ubiquitous in pharmaceuticals, natural products, medicinal compounds, and other biologically important molecules. Herein, we discussed enabling tools and technologies used for the recent C−H bonds functionalization of arenes and heteroarenes.     

Visible-light-induced 1,2-alkylarylation of alkenes with a-C(sp3)–H bonds of acetonitriles involving neophyl rearrangement under transition-metal-free conditions

An efficient visible-light-induced difunctionalization of alkenes with a-C(sp³)–H bonds of nitriles is described for the constructing of diverse 5-oxo-pentanenitriles under transition-metal-free conditions. This protocol proceeds via the functionalization of C(sp³)–H bond and radical addition/intramolecular 1,2-aryl migration processes, which features a wide scope of substituted α,α-diaryl allylic alcohols. The results of kinetic isotope experiments show that the cleavage of C(sp³)–H bond of acetonitriles is a rate-limiting step.     

Synthesis of putative clausenal from carbazole using sequential C–H borylations

A synthesis of the putative clausenal structure has been achieved from commercially available carbazole using a five-step sequence that features three iridium-catalyzed C–H borylation reactions. This conceptually disparate approach to carbazole synthesis further demonstrates the utility of the iridium-catalyzed borylation reaction in heteroaromatic C–H functionalization. The spectroscopic data of the synthetic sample casts doubt on the structure assigned to the natural product.     

Electrophotocatalytic Decarboxylative C−H Functionalization of Heteroarenes

Decarboxylative C?H functionalization reactions are highly attractive methods for forging carbon–carbon bonds considering their inherent step‐ and atom‐economical features and the pervasiveness of carboxylic acids and C?H bonds. An ideal approach to achieve these dehydrogenative transformations is through hydrogen evolution without using any chemical oxidants. However, effective couplings by decarboxylative carbon–carbon bond formation with proton reduction remain an unsolved challenge. Herein, we report an electrophotocatalytic approach that merges organic electrochemistry with photocatalysis to achieve the efficient direct decarboxylative C?H alkylation and carbamoylation of heteroaromatic compounds through hydrogen evolution. This electrophotocatalytic method, which combines the high efficiency and selectivity of photocatalysis in promoting decarboxylation with the superiority of electrochemistry in effecting proton reduction, enables the efficient coupling of a wide range of heteroaromatic bases with a variety of carboxylic acids and oxamic acids. Advantageously, this method is scalable to decagram amounts, and applicable to the late‐stage functionalization of drug molecules.